The present invention relates generally to ventilators for supporting breathing in animals. More particularly, the present invention provides a device and method of ventilating.
There are many situations in which normal breathing by an animal patient is impaired and must be assisted by external means. Oscillatory ventilators are used to facilitate breathing in such situations. Among the types of ventilators available are high frequency oscillating ventilators. U.S. Pat. No. 4,719,910 describes a high frequency oscillating ventilator. A flow of gas is conducted from a gas source to a high frequency oscillator. The high frequency oscillator comprises a housing including a magnet and having a diaphragmatically sealed piston mounted therein, an inlet connecting the space within the housing on the first side of the diaphragm to the gas conducting means, and a coil mounted to the first side of the diaphragm. Circuitry is provided which is operable to reverse the polarity of the flow of the current in the coil, thereby causing the diaphragm to move back and forth within the housing. A tube connecting the space on the second side of the diaphragm to the gas source and the patient""s airway is provided.
In the prior art, inspiratory gas is moved into and out of the patient via a U-shaped tube and movement of the diaphragm. For purposes of describing the prior art, the U-shaped tube can be described as having a first limb with a distal end, a second limb with a distal end, and a tube between the limbs. Connected to the tube between the limbs is another tube (the xe2x80x9cpatient linexe2x80x9d) that delivers gas from the U-shaped tube to the patient and also delivers gas from the patient to the U-shaped tube. The patient line may be connected to the patient via an endotracheal tube. The distal end of the first limb is placed in sealing relation to the diaphragm so that gas inside the U-shaped tube is caused to oscillate as the diaphragm moves back and forth. Gas suitable for inspiration (xe2x80x9cinspiratory gasxe2x80x9d) is supplied at a location on the U-shaped tube between the diaphragm and the patient line.
Inspiratory gas passes through the first limb of the U-shaped tube, and exhaled gas exits to the atmosphere through the second limb of the U-shaped tube and out of the distal end of the second limb. To prevent expired gases from being drawn back into the first limb during the expiratory phase of breathing, more inspiratory gas than needed by the patient is provided in order to move the expired gas into the second limb. The inspiratory gas provided in excess of the needs of the patient is referred to herein as xe2x80x9cbias flowxe2x80x9d.
To move expired gas into the second limb of the U-shaped tube, an inspiratory gas flow rate of approximately 20 liters per minute is used when ventilating infants, and as much as 60 to 80 liters per minute when ventilating older children and adults. Such large volumes of inspiratory gas would quickly exhaust the available supply of most transport and ambulance vehicles. Furthermore, such prior art devices necessitate large and costly volumes of therapeutic gases that might be mingled with the inspiratory gas (e.g., volatile anesthetics, nitric, oxide, vaporized perfluorocarbons, helium/oxygen mixtures etc.). Finally, such prior art devices are inefficient when one considers the amount of inspiratory gas required by the patient and the relatively large amount of inspiratory gas supplied to the ventilator.
An object of the present invention is to provide a device and a method of ventilating. The object is achieved by a ventilating device having an oscillator, such as an oscillatory diaphragm, and an oscillating line having a first end in sealing relationship with the oscillator. A gas supply line is connected to the oscillating line, and a patient line is connected to a second end of the oscillating line. An outlet line is in pneumatic communication with the patient line, and an end of the outlet line distal from the patient line is connected to an outlet valve. The outlet valve releases gas from the outlet line during inhalation, and prevents the release of gas from the outlet line during exhalation.
In a method according to the present invention, a ventilation device, such as the one described above, is provided. A patient in pneumatic communication with the patient line is provided and gas is supplied to the oscillating line. The oscillator is moved toward the oscillating line and the outlet valve is opened. Then, the oscillator is moved away from the oscillating line and the outlet valve is closed.